Problem in the code of using serial communication

Projects Programming
1

Hi. I was just working with the serial communication of Arduino UNO. If I press '1' , the LED on pin 13 will light and if I press '0' it will be off. What I didn't understand is that, if I put " Serial.read() - '0' == 0"
instead of the variable " val " in the condition of " else if " , it doesn't work. It prints " Invalid " even I press '0'.
Another problem is if I input multiple characters other than '1' or '0' at a time , monitor should have printed " Invalid " just once as I have used " Serial.flush () ", but it shows the message multiple times (equal to the number of characters).

The code is given below :

int LEDPIN = 13;

void setup()
{
Serial.begin(9600);
pinMode(LEDPIN,OUTPUT);
}
void loop()
{
while(Serial.available()==0);
int val = Serial.read()-'0';
if ( val == 1)
{
Serial.println("Led is ON");
digitalWrite(LEDPIN,HIGH);
}
else if (val == 0)
{
Serial.println("Led is OFF");
digitalWrite(LEDPIN,LOW);
}
else
{
Serial.println("Invalid");
}
Serial.flush();
}

serial_comm.ino (410 Bytes)

2

What's wrong with just posting the code?
It's not like you're going to bust a limit.

int LEDPIN = 13;

void setup()
{
  Serial.begin(9600);
  pinMode(LEDPIN,OUTPUT);
}
void loop()
{
  while(Serial.available()==0);
  int val = Serial.read()-'0';
  if ( val == 1)
  {
    Serial.println("Led is ON");
    digitalWrite(LEDPIN,HIGH);
  }
  else if (val == 0)
  {
    Serial.println("Led is OFF");
    digitalWrite(LEDPIN,LOW);
  }
  else 
  {
    Serial.println("Invalid");
  }
  Serial.flush();
}

It prints " Invalid " even I press '0'.

What is the serial monitor line-ending setting?

What do you think "Serial.flush()" does?

3

Nasim:
Hi. I was just working with the serial communication of Arduino UNO. If I press '1' , the LED on pin 13 will light and if I press '0' it will be off. What I didn't understand is that, if I put " Serial.read() - '0' == 0"
instead of the variable " val " in the condition of " else if " , it doesn't work. It prints " Invalid " even I press '0'.

By the time you get to your else if statement, attempting another read from serial will not give you the character that you've already read above. ( it's not in the Serial buffer anymore, once you've read it )

4

Another problem is if I input multiple characters other than '1' or '0' at a time , monitor should have printed " Invalid " just once as I have used " Serial.flush () "

What good do you think blocking until all outgoing serial data has been sent (THAT is what flush() does) will do?

5

The examples in serial input basics are simple reliable ways to receive data.

...R

6

No line ending was set in the serial monitor